2.5GHz resonance problem

Very Good

Unfortunately not so much. After closing it up the problem came back... I have to look into it again. Like Joerg already noted: it may be something 'mechanical'.

For shame!!! Been there, done that.One time, spent all afternoon 'solving' a scope probe problem!

Some of my customers disagree on the latter. If you need to run an ethernet cable through a building and have someone crimp an RJ45 connector on it you are asking for major problems. I've seen lots of problems with that. A simple screw or spring-clamp terminal is almost idiot proof.

Cool. The pcb layout looked fine to me.

Cheered too soon. It seems to be a temperature related problem in the SA.

It's an optical illusion because the picture is out of focus. Looks like the only through-hole part on there is the SMA or RP-SMA jack.

But what's wrong with through-hole parts at GHz? They wouldn't have made transistors like these if it wasn't done:

You can still buy them but at outrageous prices. I still have some one- and two-layer phenolic boards in the garage, stuff that runs up to around 800MHz. All through-hole.

Just cleaned it? Oh man, where did you get that thing from? Salvaged from a barge that sunk on the Ijsselmeer a few years ago? :-)

I have a bunch of those in my drawer. Very nice parts for the day. I was also fond of the Motorola MM8006 back in the '80s--not quite as hot as a 2N5179, but much quieter.

Cheers

Phil Hobbs

Cleaning didn't do the job... It turned out to be a crack in the coupler which is a thick film circuit on a metal carrier. The problem showed with an Ohm meter. When I loosened the screws of the thick film everything became fine, when I tightened the screws the contact opened which meant the coupler wasn't terminated.

I managed to cover the tracks with a thin layer of tin. First tests look promising...

I got it from a guy in Singapore. He probably found it in the harbour. And I mean in the water :-)

This is a case where tools and training make a real difference. Crimping works great done correctly, i know, i have done enough if it. The = average yokel cannot make good crimps without training and practice, which is where most of the problems come from. Spreading your Cat5E cable out = onto screw or spring terminals is just about guaranteed to screw up the transmission line properties. Just get 110 style punch down modular jacks, even jerks can usually get those work ok. Then you can use = factory made crimped jumper cables.

?-)

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I suspected i was seeing things that weren't there. =20 Some 30 years ago i tried to make a pulse amplifier (10 x voltage) that could do 25 volts either or both polarities into 50 ohms with 3 ns edges using TO-39 bipolar parts. Ft's were about 2.0 and 2.5 GHz.

df

Could have done it with the 2N7000. I used the BSS123 on an ultrasound machine design in 1986 because we were early SMT-adopters, no strictly technical reason. But for the pulsers we used other transistors because we needed up to 170V.

There were also a bunch of nice video-BJTs that could do it, blazingly fast and cheap. those are gone now because of the demise of the CRT technology for monitors and television sets.

Hire people who know what the hell they are doing.

Finding qualified people is very hard over here. If you know what you are doing you are in management! The unemployment rates are still very low over here. Low enough to keep loads of East-European people working as well. Example: when they came to connect the optic-fiber in my house they send a Polish guy and two Dutch guys. The Polish guy had to explain to the Dutch guys how to drill a hole in concrete! The Polish guy also welded the optic fibers and did the final testing.

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Alas, unless i wanted to dip into my own pocket or do a lot of paperwork = i had a rather limited selection of transistors and ICs to build with.

?-)

Paperwork to get engineering parts? I guess I wouldn't have stuck it out at that company for very long :-)

Did they at least allow you to order free samples?

At the PPoE, they made us submit reqs for SMT resistors. They thought they could keep the inventory, or something. Of course it ended up being just something else to keep the admin busy and engineering from doing it's job. Hey, they're $.002 each!

I'm almost embarrassed at the samples I get now. There are sometimes enough that I would have had enough for the entire production run at the PPoE. ;-)

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Never had occasion to try. Guess the selection wasn't all that limited. The few times i needed something exotic, like CA3308 flash ADCs shortly after they came out, i could get them.

?-)